1. Field of the Invention
The present invention relates generally to a driving circuit which drives and controls a voltage control type power switching element so as to perform a switching operation in the power switching element by applying a voltage to a gate of the power switching element while controlling the voltage in response to an output pulse, and more particularly to a driving circuit having a first switching element, which sets a charging line at a conductive state to supply a positive or negative electric charge to the gate of the power switching element through the charging line in response to each first edge of the output pulse such as leading edge or trailing edge, and a second switching element, which sets a discharging line at a conductive state to discharge the supplied charge from the gate of the power switching element through the discharging line in response to each second edge of the output pulse.
2. Description of Related Art
Published Japanese Patent First Publication No. 2005-151700 discloses a driving circuit for a main switching element. In this circuit, the main switching element is driven in synchronization with each edge of an output pulse of a transformer. More specifically, a p-channel transistor of the driving circuit is turned on in synchronization with each leading edge of the output pulse to supply a positive electric charge to a gate of the switching element through the p-channel transistor, and an n-channel transistor of the driving circuit is turned on in synchronization with each trailing edge of the output pulse to discharge the supplied charge from the gate of the switching element through the n-channel transistor. Therefore, a positive voltage and a negative voltage can alternately be applied to the gate of the switching element, so that the driving circuit can drive the switching element so as to perform a switching operation in the switching element.
However, both of the p-channel and n-channel transistors are inevitably turned on together during an overlap period of time. Therefore, a large amount of current passes through the p-channel and n-channel transistors as a through current, so that reliability of the driving circuit is lowered.
Further, an other driving circuit has been proposed. This circuit has a first switching element, which sets a charging line at a conductive state in response to each leading edge of an output pulse generated in a transformer to supply a positive electric charge to a gate of a power switching element through the charging line, and a second switching element which sets a discharging line at a conductive state in response to each trailing edge of the output pulse to discharge the supplied charge from the gate of the power switching element. In this circuit, a through current flows through the conducting elements during an overlap period of time, in the same manner. Therefore, reliability of the driving circuit is also lowered.